The Facility for Element Analysis of Microdroplets provides investigators within the Renal Center with the capability of analyzing the element composition of extremely small biological fluid samples. Specimen which can be analyzed in this way include the perfusate obtained from isolated perfused tubular segments and droplets obtained by micropuncture. In most cases, the size of the fluid samples precludes the analysis by any other known method. The availability of this facility as a Center Core will guarantee a short turnover time and provide the investigators with an immediate feedback of the experimental results. Furthermore, potential problems associated with the shipping of fluid samples are avoided.